Home-sharing site Airbnb has its share of critics, from neighbors who hate the idea of strangers in their building or on their block, to traditional hotels that want Airbnb hosts to receive the same tax treatment and regulatory scrutiny they do, to, of course, the occasional creep-out victims. But another consistent argument is of the bigger-picture variety: that Airbnb drives up rents in cities where housing costs are already staggering.